Improvements in fuel economy for heavy duty diesel engines have generally been achieved either through new engine design or through new approaches to lubricating oil formulating. Lubricant optimization is especially preferred over engine hardware changes due to its comparative lower cost per unit in fuel efficiency and possibility for backward compatibility with older engines. Organic friction modifiers, such as fatty acid esters, fatty acid amides, fatty amines, and the like, have been widely used in passenger car motor oils to reduce the energy losses due to friction in the various parts of the engine and to prevent engine wear thereby improving fuel economy. However, lubricating oil compositions containing these organic friction modifiers have not proven to be effective in diesel engines due to the different lubrications conditions found in diesel engines.
To improve fuel efficiency in heavy duty diesel engines, there has been a drive to develop new components which improve the frictional properties of the lubricating oil composition.
U.S. Pat. No. 828,733 discloses copper salts of hindered phenolic carboxylic acids.
U.S. Pat. No. 3,873,278 discloses an amine carboxylate salt derived from tall oil fatty acid and a C12-18 alkyl or alkenyl amine containing about 3-7 oxyethylene groups which provide anti-stalling, anti-icing, anti-corrosion and detergent properties in motor fuels or gasoline.
U.S. Pat. No. 4,231,883 discloses the use of alkoxylated hydrocarbyl amine in a lubricating oil or fuel to reduce friction in an internal combustion engine. An example of the alkoxylated amine compounds that are disclosed is N,N-bis(2-hydroxyethyl)oleylamine.
U.S. Pat. No. 4,382,006 discloses a lubricating composition containing a friction reducing portion of a borated adduct of compounds which includes “Ethomeens”. Borated salts of tertiary amines are disclosed as cutting fluids in U.S. Pat. No. 3,186,946.
WO 94/19434 discloses lubricating oil compositions containing alkoxylated amine salts of hydrocarbylsaliclic acids, hydrocarbylsulfonic acids, dihydrocarbyldithiophosphoric acids or dihydrocarbyldithiobenzoic acids trithiocyanuric acid which are stated to improve frictional properties. See also U.S. Pat. Nos. 5,330,666; 5,320,767; 5,320,766; and 5,308,518; respectively.
U.S. Pat. No. 5,078,893 discloses a lubricating composition adaptable for use as a power transmitting fluid having a lubricating oil, a friction modifying amount of a borated or unborated alkoxylated amine and an amount of organic phosphate ester effective to impart both antiwear and friction modification to the composition.
U.S. Pat. No. 7,691,764 discloses lubricating and fuel compositions containing metal free detergents prepared from the reaction product of an acidic organic compound, a boron compound and an amine The acid organic compound exemplified is a hydrocarbyl salicylic acid.